Extract frames from .evo files/movies

Question

I'm trying to extract frames from a .evo files.

I tried .VideoCapture from the cv2 module. It did extract frames but they were all grey.

I also used ffmpeg in the terminal to convert the .evo in a .mp4 movie -> Same result, just movie with only grey frames.

My question is: is it possible to convert an .evo file in a .mp4/.mov format for instance ? If yes, How ?

Thanks in advance everyone !